/*

??binsearch.c?-?general?binary?search?functions

*/

#include?
#include?

static?char?*Id?=?“$Id:?binsrch.cv?1.15?2005/02/01?16:46:43?wn?Rel?$“;

/*?Binary?search?-?looks?for?the?key?passed?at?the?start?of?a?line
???in?the?file?associated?with?open?file?descriptor?fp?and?returns
???a?buffer?containing?the?line?in?the?file.?*/

#define?KEY_LEN		（1024）
#define?LINE_LEN	（1024*25）

static?char?line[LINE_LEN];?
long?last_bin_search_offset?=?0;

/*?General?purpose?binary?search?function?to?search?for?key?as?first
???item?on?line?in?open?file.??Item?is?delimited?by?space.?*/

#undef?getc

char?*read_index（long?offset?FILE?*fp）?{
????char?*linep;

????linep?=?line;
????line[0]?=?‘0‘;

????fseek（?fp?offset?SEEK_SET?）;
????fgets（linep?LINE_LEN?fp）;
????return（line）;
}

char?*bin_search（char?*searchkey?FILE?*fp）
{
????int?c;
????long?top?mid?bot?diff;
????char?*linep?key[KEY_LEN];
????int?length;

????diff=666;
????linep?=?line;
????line[0]?=?‘\0‘;

????fseek（fp?0L?2）;
????top?=?0;
????bot?=?ftell（fp）;
????mid?=?（bot?-?top）?/?2;

????do?{
	fseek（fp?mid?-?1?0）;
	if（mid?!=?1）
	????while（（c?=?getc（fp））?!=?‘\n‘?&&?c?!=?EOF）;
????????last_bin_search_offset?=?ftell（?fp?）;
	fgets（linep?LINE_LEN?fp）;
	length?=?（int）（strchr（linep?‘?‘）?-?linep）;
	strncpy（key?linep?length）;
	key[length]?=?‘\0‘;
	if（strcmp（key?searchkey）?	????top?=?mid;
	????diff?=?（bot?-?top）?/?2;
	????mid?=?top?+?diff;
	}
	if（strcmp（key?searchkey）?>?0）?{
	????bot?=?mid;
	????diff?=?（bot?-?top）?/?2;
	????mid?=?top?+?diff;
	}
????}?while（（strcmp（key?searchkey））?&&?（diff?!=?0））;
????
????if（!strcmp（key?searchkey））
	return（line）;
????else
	return（NULL）;
}

static?long?offset;

static?int?bin_search_key（char?*searchkey?FILE?*fp）
{
????int?c;
????long?top?mid?bot?diff;
????char?*linep?key[KEY_LEN];
????int?length?offset1?offset2;

????/*?do?binary?search?to?find?correct?place?in?file?to?insert?line?*/

????diff=666;
????linep?=?line;
????line[0]?=?‘\0‘;

????fseek（fp?0L?2）;
????top?=?0;
????bot?=?ftell（fp）;
????if?（bot?==?0）?{
	offset?=?0;
	return（0）;		/*?empty?file?*/
????}
????mid?=?（bot?-?top）?/?2;

????/*?If?only?one?line?in?file?don‘t?work?through?loop?*/

????length?=?0;
????rewind（fp）;
????while（（c?=?getc（fp））?!=?‘\n‘?&&?c?!=?EOF）
	line[length++]?=??c;
????if?（getc（fp）?==?EOF）?{	/*?only?1?line?in?file?*/
	length?=?（int）（strchr（linep?‘?‘）?-?linep）;
	strncpy（key?linep?length）;
	key[length]?=?‘\0‘;
	if（strcmp（key?searchkey）?>?0）?{
	????offset?=?0;
	????return（0）;		/*?line?with?key?is?not?found?*/
	}?else?if?（strcmp（key?searchkey）?	????offset?=?ftell（fp）;
	????return（0）;		/*?line?with?key?is?not?found?*/
	}?else?{
	????offset?=?0;
	????return（1）;		/*?line?with?key?is?found?*/
	}
????}

????do?{
	fseek（fp?mid?-?1?0）;
	if（mid?!=?1）
	????while（（c?=?getc（fp））?!=?‘\n‘?&&?c?!=?EOF）;
	offset1?=?ftell（fp）;	/*?offset?at?start?of?line?*/
	if?（fgets（linep?LINE_LEN?fp）?!=?NULL）?{
??	????offset2?=?ftell（fp）;?/*?offset?at?start?of?next?